Impact of shock energy and ventricular rhythm on the success of first shock therapy: The ALTITUDE first shock study.

MedLine Citation:

PMID:
23337541
Owner:
NLM
Status:
Publisher

Abstract/OtherAbstract:

BACKGROUND: The efficacy of shock in converting different ventricular tachyarrhythmias has not been well characterized in a large, natural-practice setting. OBJECTIVE: To determine shock success rate by energy and ventricular rhythm in a large cohort of patients with implantable cardioverter defibrillators (ICD). METHODS: Two thousand patients with 5279 shock episodes were randomly sampled for analysis from the LATITUDE remote monitoring system. Within an episode, the rhythm preceding therapy (shock or antitachycardia pacing (ATP) was adjudicated. Patients who died after unsuccessful ICD shocks did not transmit final remote monitoring data and were not included in the study. RESULTS: Of 3677 shock episodes for ventricular tachyarrhythmia, 2679 were treated with shock initially and were classified as monomorphic (MVT, N=1544), polymorphic ventricular tachycardia (MVT/PVT, N=371), or ventricular fibrillation (VF, N=764). First, second and final shock success averaged 90.3%, 96.4% and 99.8 %, respectively. After unsuccessful initial ATP (n=998), the first, second and final shock was successful in 84.8%, 92.9% and 100% of episodes. Success after the first or second shock was significantly lower after failed ATP compared to shock as initial therapy (both p<.001). Among episodes treated with shock initially, the success rate for MVT (89.2%) when treated with energy level ≤20 J was significantly higher than VF (80.8%, p=.04). The level of shock energy was a significant predictor of the success of the first shock (OR =1.16, 95% CI 1.03-1.30, p=.013). CONCLUSION: The first shock success rate as an initial therapy is approximately 90%, but was lower following failed ATP. Programming a higher level of energy after ATP is suggested.